Nuclear mass flowmeter

ABSTRACT

A flowmeter utilizing a Beta source positioned upstream of a cylindrical capacitor formed by two spaced-apart concentric cylindrical sections. The concentric cylindrical sections form the capacitor electrodes and they are a part of two concentric, inner and outer, tubular members which are mounted in an outer housing that is adapted to be connected into a flow line so that fluid flows through both the inner and outer tubular members. The capacitor electrodes are insulated from the tubular members by means of dielectric ring members connected therebetween. Means are provided for detecting any potential difference between the two electrodes and for evacuating the space between the outer tubular member and the housing.

bit States Pate [72] Inventor Thomas N. Marshall, Jr.

Huntsville, Ala.

[21] Appl. No. 22,320

[22] Filed Mar. 24, 1970 [45] Patented Aug. 17, 1971 [73] Assignee TheUnited States of America as represented by the Administrator of theNational Aeronautics and Space Administration [54] NUCLEAR MASSFLOWMIETER 8 Claims, 2 Drawing Figs.

[52] 11.5. C1 73/194 F, 250/435 FC [51] Int. Cl G01f1/00 [50] Field ofSearch 73/194 E, 194 R194 M; 250/836 FT, 43.5 PC, 106 T [56] References(Iited UNITED STATES PATENTS 1,808,709 6/1931 Blake 73/194(F) PrimaryExaminer-Charles A. Ruehl Att0rneys L. D. Wofford, .lr., Charles C.Wells and John R.

Manning ABSTRACT: A flowmeter utilizing a Beta source positionedupstream of a cylindrical capacitor formed by two spacedapart concentriccylindrical sections. The concentric cylindrical sections form thecapacitor electrodes and they are a part of two concentric, inner andouter, tubular members which are mounted in an outer housing that isadapted to be con nected into a flow line so that fluid flows throughboth the inner and outer tubular members. The capacitor electrodes areinsulated from the tubular members by means of dielectric ring membersconnected therebetween. Means are provided for detecting any potentialdifference between the two electrodes and for evacuating the spacebetween the outer tubular member and the housing.

PATENTED AUG] 7 I97! QMFMEOWEUMJM ATTORNEYS NUCLEAR MASS FLOW/METERBACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to flow meters and in particular the invention is intended forthe measurement of mass flow of a nonpolar liquid like, for example,liquid hydrogen.

2. Description of the Prior Art Prior art flow meters have generallybeen of the type that measured the flow velocity of the liquid throughconduit by placing some type of movable element in the flow. This gave avelocity or volumetric flow measurement. In order to obtain mass flowrates it was necessary to make a separate measurement of the fluiddensity and combine this with the volumetric flow rates to inferentiallyarrive at the mass flow rate. These prior art techniques werecumbersome. Also, in monitoring the flow ofa fluid the use ofa movableelement in the flowis not desirable because among other things, themovable element will deteriorate with time changing its characteristics.Another objectionable feature of prior art devices and techniques isthat a power source is needed and in many cases complicated readoutequipment is required.

SUMMARY OF THE INVENTION The present invention is a flowmeter capable ofmeasuring the mass flow rates of a nonpolar fluid like liquid hydrogen.The device in general is a cylindrical conduit made up of two spacedapart concentric tubular members having sections that form a cylindricalcapacitor. A source of Beta particles is located upstream of thecapacitor.

The fluid to be monitored flows through both tubular members and thesetubular members are mounted in an outer hous ing having mounting flangesat each end thereof adapted for connection into a fluid flow line.Adjacent one of their ends the tubular members each have a pair ofspaced dielectric ring members mounted therein. Placing these rings ineach tubular member forms a cylindrical section which is electricallyisolated from the remainder of the tubular member. The electricallyisolated section in each tubular member forms one electrode of acylindrical capacitor. Included are electrical contact means in contactwith these isolated sections to permit connection of externally locatedelectrical devices to the clectrodes of the cylindrical capacitor.

The Beta source is mounted in the inner tubular member in a positionbetween the cylindrical capacitor and the upstream end of the flowmeter.The positioning of the Beta source is such that it is spaced away fromthe cylindrical capacitor and also the upstream end of the inner andouter tubular members a distance that is greater than the distance theBeta particles can travel from the Beta source before being absorbed bya nonflowing liquid filling the flowmeter. As fluid flows through thedevice some of the flowing molecules will acquire a negative electricalcharge when a Beta particle attaches thereto. This will in turn resultin the inner-electrode of the capacitor undergoing a change in potentialinversely proportional to the velocity of the fluid, i.e., becomingnegative, relative to the outer electrode. The potential differencebetween the two electrodes can be measured to obtain an indication ofthe mass flow rate. The potential difference between the two electrodeswill be effected by the dielectric constant of any materials positionedbetween the two electrodes. Inasmuch as there will be fluid flowingbetween the inner and outer tubular members and since the dielectricconstant of the fluid positioned between the two electrodes will varywith the density of the flowing fluid, the fluid flowing between the twoelectrodes will affect the potential difference between the inner andouter electrodes of the cylindrical capacitor.

If the fluid flow being monitored did not pass between the twoelectrodes; i.e., was allowed to flow only through the inner tubularmember, then only a velocity measurement could be made. By passing themonitored flow through the electrodes the capacitance of the cylindricalcapacitor is made dependent upon the density of the flowing fluid andthis makes possible a mass measurement.

It is therefore an object of the invention to provide a flowmeter whichcan function without an external power supply or source of excitation.

A further object is to provide a flowmeter which has no moving parts anddoes not require complicated readout equipment.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a pictorial view, partiallybroken away and sectioned, illustrating a flowmeter constructed inaccordance with the invention;

FIG. 2 is a cross-sectional elevational view showing the internaldetails of the flowmeter.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 of thedrawing, a flowmeter is illustrated pictorially that includes an outerhousing 10 having mounting flanges 12 and 14 on the ends thereofforconnecting the flowmeter into a fluid flow line (not shown). A pair oftubular members, inner tubular member 116 and outer tubular member 18,are positioned within the outer housing. Outer tubular member 18 issecured in position to mounting flanges l2 and 14 by the use ofadhesives, welding or the like. Spokelike spacers 20 are mounted betweenthe inner and outer tubular members near the ends thereof. The purposeof the spacers is to hold the inner tubular member in position and thespacers can be attached by welding, brazing or other suitable means. Thespace between the inner nd outer tubular members forms an annularchamber 22 which is in communication withthe upstream end of theflowmeter by means of annular opening 24. Chamber 22 is in communicationwith the downstream end of the flowmeter through annular opening 26. Itshould be noted that the spacers 20 are spokelike and do not interfereto any extent with the flow of fluid from the flow line into the annularchamber 22.

The outer tubular member is provided with a pair of spaced ring members28 and 30 mounted in the outer tubular member in such manner, by weldingor the use of adhesives, as to form an integral part thereof. These ringmembers are composed of a suitable dielectric material, ceramic forexample, so that they electrically isolate a section 32 of the outertubular member from the remainder of the tubular member. Inner tubularmember 16 is provided with dielectric ring members 34 and 36 so as toprovide a similarly electrically isolated section 38 in tubular member16. Sections 32 and 38 of the tubular members form a cylindricalcapacitor with these sections being the electrodes of the capacitor. Thedielectric would be the liquid that normally fills the space between thetwo elec trodes.

An electrical feed-through 40 mounted in housing 10 extends inwardlythrough the outer tubular member 18. Feedthrough $0 is composed of aninsulating material and has a conductor 42 passing through the centerthereof that is in electrical contact with electrode 38. A similarelectrical feedthrough 44 is mounted in housing It) and has a conductor46 passing through the center thereof that is in electrical contact withelectrode 32. Conductors 42 and 46 are connected to an electrometer 48for reading out any potential difference that exists between electrodes32 and 38.

A Beta source 50 is positioned within the inner tubular member betweenthe cylindrical capacitor section and the upsteam end of the inner andouter tubular members. Strontium or other radio active substances couldbe used as a Beta source. The position of the Beta source must be suchthat its distance from the upstream end of the cylindrical capacitor andalso from the annular opening 24 into chamber 22 exceeds the distancethat a Beta particle from the Beta source can travel in a nonflowingliquid without being absorbed by the nonflowing fluid. In other words,if the flowmeter is filled with a fluid it is essential that none of theBeta particles be able to enter the annular opening and flow intochamber 22 so as to affect the electrical charge in the area betweenelectrodes 32 and 38. Likewise, in a nonflowing fluid it is necessarythat none of the Beta particles reach the internal electrode 38 of thecylindrical capacitor so as to affect the potential difference betweenthe two electrodes of the capacitor. This can be accomplished only ifthe Beta source is positioned such that in a nonflowing liquid thecharge of the Beta particle will be absorbed or neutralized by theliquid before it can reach electrode 38 or the annular chamber 22.

A vacuum pump 52 is connected to housing via inlet 54 for evacuatingchamber 56. Chamber 56 is formed by housing 10, mounting flanges 12 and14, and outer tubular member 18.

As mentioned above the capacitance of the cylindrical capacitor willdepend upon the dielectric constant of the fluid positioned between thetwo electrodes. Further the dielectric constant of the fluid between theelectrodes will vary with density of the fluid. This fact is what makesit possible to obtain a mass measurement rather than just a velocitymeasurement. The velocity measurement could be made with flow onlythrough the inner tubular member. In order to reduce the effect ofambient conditions chamber 56 is evacuated so as to reduce heat transferbetween outer tubular member 18 and its surroundings. This would beparticularly important when the fluid flow being measured was that of acryogenic liquid like liquid hydrogen.

In operation the flowmeter would be mounted in a fluid flow line, theelectrodes of the cylindrical capacitor connected to an electrometer orother suitable readout device, and chamber 56 evacuated. Liquid flowwould enter the device through the upstream end thereof and flow intoannular chamber 32 and through tubular member 16. As the liquid passesthe Beta source, Beta particles will attach to some of the liquidmolecules giving that molecule the charge of an electron, a negativecharge. As the negatively charged molecules flow through theelectrically isolated section of tubular member 16, that is electrode38, the electrode acquires a negative charge with respect to electrode32. The potential difference across the electrodes will vary withchanges in flow velocity through tubular member 16 and changes in thedielectric constant of the fluid between the electrodes due to changesin the density of the flowing liquid. These potential differences can beread out on the Electrometer to provide a mass flow measurement.

What I claim is:

l. A device for measuring the mass flow of a nonpolar fluid through afluid flow line comprising:

a housing adapted to be connected into said flow line so as to have anupstream and a downstream end and receive a flow of fluid therethrough;

an outer tubular member mounted in said housing that includes anelectrically isolated section that forms a first electrode ofacylindrical capacitor;

an inner tubular member mounted within said outer cylindrical memberthat also includes an electrically isolated section that forms a secondelectrode of a cylindrical capacitor, said second electrode being equalin length to said first electrode and in longitudinal alignmenttherewith;

mounting means attached between said inner and outer tubular members forsupporting the inner tubular member in a spaced position with respect tothe outer tubular member whereby fluid can flow between the inner andouter tubular members as well as through the inner tubular member;

source means mounted in said inner tubular member for altering theelectrical charge of the fluid molecules in the fluid flow through theinner tubular member which in turn results in a difference in electricalpotential between said first and second electrodes that is indicative ofthe mass flow offluid through the device; and detecting means fordetecting the difference in electrical potential between said first andsecond electrodes. 2. The device recited in claim 1 which furtherincludes control means for controlling the atmosphere in the spacebetween said housing and said outer tubular member.

3. The device recited in claim 2 wherein said control means is a vacuumpump connected into the space between said housing and said outertubular member for pulling a vacuum therein.

4. The device recited in claim 3 wherein said source means emits Betaparticles that attach to at least some of the molecules of the flowingfluid resulting in these molecules acquiring the charge of an electron,whereby the flow of such fluid through said second electrode will causesaid second electrode to acquire a negative potential with respect tosaid first electrode.

5. The device recited in claim 4 wherein: said source means is mountedin said inner tubular member in a position between the second electrodeand the upstream end ofsaid device;

said source means being spaced away from said first electrode and theupstream end of said inner and outer cylindrical members a distancegreater than the distance the Beta particles from said source means cantravel in the fluid being monitored when it is not flowing.

6. The device recited in claim 5 wherein said first and secondelectrodes are each formed by a pair of spaced dielectric ring membersmounted in each of said inner and outer tubular members so as to formtwo spaced and concentric tubular members that are the electrodes of theabove recited cylindrical capacitor, the capacitance of said cylindricalcapacitor being determined by the dielectric constant of the fluidpresent between the two electrodes.

7. The device recited in claim 6 wherein said detecting means includes:

a pair of electrical connectors mounted in said housing and insulatedtherefrom;

one of said connectors extending through said first electrode, and beinginsulated therefrom, so as to be in electrical connection with saidsecond electrode; and

the other of said connectors being in electrical contact with said firstelectrode.

8. The device recited in claim 7 which further includes an electrometerconnected to said pair of electrical connectors for detecting anyelectrical potential difference between said first and secondelectrodes.

1. A device for measuring the mass flow of a nonpolar fluid through afluid flow line comprising: a housing adapted to be connected into saidflow line so as to have an upstream and a downstream end and receive aflow of fluid therethrough; an outer tubular member mounted in saidhousing that includes an electrically isolated section that forms afirst electrode of a cylindrical capacitor; an inner tubular membermounted within said outer cylindrical member that also includes anelectrically isolated section that forms a second electrode of acylindrical capacitor, said second electrode being equal in length tosaid first electrode and in longitudinal alignment therewith; mountingmeans attached between said inner and outer tubular members forsupporting the inner tubular member in a spaced position with respect tothe outer tubular member whereby fluid can flow between the inner andouter tubular members as well as through the inner tubular member;source means mounted in said inner tubular member for altering theelectrical charge of the fluid molecules in the fluid flow through theinner tubular member which in turn results in a difference in electricalpotential between said first and second electrodes that is indicative ofthe mass flow of fluid through the device; and detecting means fordetecting the difference in electrical potential between said first andsecond electrodes.
 2. The device recited in claim 1 which furtherincludes control means for controlling the atmosphere in the spacebetween said housing and said outer tubular member.
 3. The devicerecited in claim 2 wherein said control means is a vacuum pump connectedinto the space between said housing and said outer tubular member forpulling a vacuum therein.
 4. The device recited in claim 3 wherein saidsource means emits Beta particles that attach to at least some of themolecules of the flowing fluid resulting in these molecules acquiringthe charge of an electron, whereby the flow of such fluid through saidsecond electrode will cause said second electrode to acquire a negativepotential with respect to said first electrode.
 5. The device recited inclaim 4 wherein: said source means is mounted in said inner tubularmember in a position between the second electrode and the upstream endof said device; said source means being spaced away from said firstelectrode and the upstream end of said inner and outer cylindricalmembers a distance greater than the distance the Beta particles fromsaid source means can travel in the fluid being monitored when it is notflowing.
 6. The device recited in claim 5 wherein said first and secondelectrodes are each formed by a pair of spaced dielectric ring membersmounted in each of said inner and outer tubular members so as to formtwo spaced and concentric tubular members that are the electrodes of theabove recited cylindrical capacitor, the capacitance of said cylindricalcapacitor being determined by the dielectric constant of the fluidpresent between the two electrodes.
 7. The device recited in claim 6wherein said detecting means includes: a pair of electrical connectorsmounted in said housing and insulated therefrom; one of said connectorsextending through said first electrode, and being insulated therefrom,so as to be in electrical connection with said second electrode; and theother of said connectors being in electrical contact with said firstelectrode.
 8. The device recited in claim 7 which further includes anelectrometer connected to said pair of electrical connectors fordetecting any electrical potential difference between said first andsecond electrodes.